<style>
    button {
        border-radius: 5px;
        color: white;
        background-color: #0F5897;
        padding: 5px 10px 8px 10px;
    }
    button:hover {
        animation-name: background-color;
        animation-duration: 500ms;
        /* add your code below this line */
        animation-fill-mode: forwards;
        /* add your code above this line */
    }
    @keyframes background-color {
        100% {
            background-color: #4791d0;
        }
    }
</style>
<button>注册</button>